1. Field of the Invention
The invention relates to the vapor phase catalytic oxidation of unsaturated aliphatic aldehydes to the corresponding unsaturated aliphatic carboxylic acids.
2. Description of the Prior Art
The use of molybdenum and vanadium containing catalyst systems for the gas phase oxidation of alpha-beta unsaturated aliphatic aldehydes, such as acrolein, to the corresponding alpha-beta-unsaturated carboxylic acids, such as acrylic acid, has been known.
In these reactions a gaseous reaction mixture which usually contains the aldehyde, molecular oxygen and water, as steam, is brought into contact with the catalyst, by continuously passing a stream of the reaction mixture through a bed of the catalyst. Such known catalyst systems would include those disclosed in the following U.S. Pat. Nos.: 3,087,964; 3,358,020; 3,408,392; 3,435,069; 3,439,028; 3,530,175; 3,567,772; 3,567,773; 3,574,729; 3,644,509; 3,655,749; 3,670,017 and 3,703,548. Not all of these catalyst systems, however, are currently useful for commercial purposes. Some of these catalyst systems, for example, do not provide the relatively high levels of % conversion, productivity and % selectivity, which are all required, presently, of a commercially useful catalyst system.
The terms % conversion, productivity, and % selectivity which are employed herein with respect to the present invention are defined as follows: ##EQU1##